The present invention relates to apparatus for testing the condition and/or other characteristics of cigarettes, cigarillos, cigars, filter rod sections, cheroots or other types of rod-shaped articles which constitute or form part of smokers' products. More particularly, the invention relates to improvements in apparatus for testing groups of parallel or substantially parallel cigarettes or analogous rod-shaped articles, for example, in a packing machine wherein arrays consisting of predetermined numbers of cigarettes are introduced into soft packs, flip-top (hinge lid) packs or other types of containers.
It is already known to test groups of cigarettes which are about to be introduced into packs consisting of one or more layers of paper, metallic foil, cardboard or like wrapping material. The groups of cigarettes are tested for several reasons, e.g., to ascertain whether or not each and every group contains a requisite number of cigarettes, whether or not the cigarettes of each group are properly oriented with respect to each other, whether or not each and every cigarettes of a group has a satisfactory tobacco-containing end, whether or not the ends of wrappers of the cigarettes are frayed or otherwise damaged, and/or for other reasons. The two main reasons for the testing of such groups are (a) to ascertain whether or not each group contains a required number of articles and (b) whether or not the cigarettes of a group are formed with satisfactory tobacco-containing ends.
U.S. Pat. No. 3,116,478 granted Dec. 31, 1963 to Powell discloses a testing apparatus wherein a housing defines a chamber for a reciprocable sensing pin. The chamber is connected with a pneumatic monitoring unit which ascertains whether or not the tobacco-containing end of a cigarette (against which the sensing pin has been advanced) is satisfactory. The sensing pin is biased by a suitable spring which yields when the housing is moved toward a cigarette, or vice versa, so that the sensing pin engages with and is displaced by the cigarette. The sensing pin has an axial bore and several transverse bores which allow the chamber to communicate with the atmosphere in extended position of the pin. If the pin is pushed into the housing by a satisfactory cigarette in the course of a testing operation, the bores cannot connect the chamber with the atmosphere and the monitoring unit cannot generate a signal which denotes that the tested cigarette is defective or absent. The open ends of the aforementioned bores are then sealed by a wall of the housing whereby the pressure in the chamber increases, and such pressure is propagated into the monitoring unit to indicate that the article which is in the process of being treated is acceptable. The apparatus which is illustrated in the aforementioned patent is intended for testing of discrete cigarettes, i.e., for testing of one cigarette at a time. However, the patent also mentions the possibility of using several sensing pins for simultaneous testing of a plurality of cigarettes.
The just discussed patented testing apparatus exhibits several drawbacks. First of all, and as shown in FIG. 3 of the patent, the sensing pin is a precision-finished component whose manufacturing cost is relatively high. The sensing pin must be received in its bore with a minimum of clearance so as to avoid leakage of air and attendant fluctuations of pressure in the interior of the chamber. Were the illustrated apparatus provided with several sensing pins, fluctuations of pressure in the chamber would be compounded in response to leakage of air between the peripheral surfaces of the sensing pins and the surfaces surrounding the respective bores therefor. Even a minor deviation of air pressure in the chamber from the optimum pressure is likely to entail the generation of a "defect" signal with the result that the tested cigarette or the tested group of cigarettes is expelled from the packing machine or is otherwise segregated from other cigarettes or groups of cigarettes. Improper sealing of or by a single sensing pin would suffice to initiate the segregation and discarding of an entire group of cigarettes, e.g., of an array of twenty cigarettes which are about to be introduced into a soft pack or a like container. Furthermore, the bores in the sensing pin or pins cannot be selected at will, especially as regards their maximum diameters, because the diameter of the sensing pin is relatively small (such diameter is or should be less than the diameter of a cigarette, especially if two or more sensing pins are to be placed sufficiently close to each other for simultaneous testing of the ends of a block or group of cigarettes in an array which is customary in a cigarette pack wherein the wrappers of neighboring cigarettes actually contact each other). In such instances, the diameters of each sensing pin must be at least slightly less than the diameter of a cigarette in order to provide room for the guide means wherein the pins are slidable during engagement with the tobacco-containing ends of satisfactory cigarettes. The making of small-diameter bores in sensing pins is expensive and time-consuming. Also, the mass of the sensing pins cannot be reduced at will even though lightweight sensing pins are desirable in order to allow to rapid movement in directions toward or away from one or more cigarettes to be tested. The difficulty of making small-diameter bores in small-diameter sensing pins is one of the factors which limits the extent to which the mass of a sensing pin can be reduced. Lightweight sensing pins are particularly desirable in modern high-speed packing machines which turn out many hundreds of packs per minute and, therefore, the apparatus which tests the ends of groups or blocks of cigarettes must test several thousand cigarettes per minute. Relatively heavy sensing pins are likely to cause the monitoring means to furnish inaccurate readings which results in rejection of numerous satisfactory groups of cigarettes or in introduction of unsatisfactory groups into packs or like containers.